Jasmonates(JAs),a class of lipid-derived stress hormones,play a crucial role across an array of plant phys-iological processes and stress responses.Although JA signaling is thought to rely predominantly on the degradation of specific JAZ proteins by SCFCOI1,it remains unclear whether other pathways are involved in the regulation of JAZ protein stability.Here,we report that PUB22,a plant U-box type E3 ubiquitin ligase,plays a critical role in the regulation of plant resistance against Helicoverpa armigera and other JA re-sponses in tomato.Whereas COI1 physically interacts with JAZ1/2/5/7,PUB22 physically interacts with JAZ1/3/4/6.PUB22 ubiquitinates JAZ4 to promote its degradation via the 26S proteasome pathway.Impor-tantly,we observed that pub22 mutants showreduced resistance to H.armigera,whereasjaz4 single mu-tants and jaz1 jaz3 jaz4 jaz6 quadruple mutants have enhanced resistance.The hypersensitivity of pub22 mutants to herbivores could be partially rescued by JAZ4 mutation.Moreover,we found that expression of PUB22 can be transcriptionally activated by MYC2,thus forming a positive feedback circuit in JA signaling.We noticed that the PUB22-JAZ4 module also regulates other JA responses,including defense against B.cinerea,inhibition of root elongation,and anthocyanin accumulation.Taken together,these re-sults indicate that PUB22 plays a crucial role in plant growth and defense responses,together with COI1-regulated JA signaling,by targeting specific JAZs.

薄荷作为药食同源植物,具有重要经济价值.茉莉酸信号抑制子JAZ蛋白在调节植物应答逆境胁迫方面具有重要作用.克隆薄荷MeJAZ8基因,并分析其蛋白特征、蛋白互作和表达模式,为薄荷抗逆分子育种提供基因资源.该实验将通过生物信息学、酵母双杂交、烟草叶片瞬时表达、qRT-PCR等技术对McJAZ8的蛋白结构特征、亚细胞定位、蛋白互作与基因表达进行分析.结果显示:①McJAZ8基因全长543 bp,编码180个氨基酸,McJAZ8蛋白具有保守的TIFY和Jas结构域,与拟南芥AtJAZ1和AtJAZ2同源性较高.②McJAZ8蛋白定位于细胞核和细胞质.③酵母双杂交结果显示,McJAZ8与其自身或Mc-JAZ1/3/4/5蛋白互作形成同源或异源二聚体.④McJAZ8在不同组织中均有表达,幼叶中表达量最高.在叶序中,McJAZ8在第4片叶中表达量最高,而第2片叶中表达量最低.⑤在叶片和根中,McJAZ8在茉莉酸甲酯(MeJA)、干旱、NaCl处理下的表达呈不同程度地上调;McJAZ8的表达在CdCl2处理下呈先上调而后下调的模式;在叶片中,McJAZ8的表达在CuCl2处理下呈逐渐下调的趋势,而在根中呈先下调后上调再下调的趋势;在叶片和根中,MeJAZ8在A1C13处理下的表达均呈不同程度的下调.该研究丰富了薄荷中茉莉酸信号抑制子JAZ基因的研究,并为薄荷分子育种提供了基因资源.

Salt stress is a major abiotic stress which severely hinders crop production.However,the regulatory network controlling tomato resistance to salt remains unclear.Here,we found that the tomato WRKY transcription factor WRKY57 acted as a negative regulator in salt stress response by directly attenuating the transcription of salt-responsive genes(SlRD29B and SlDREB2)and an ion homeo-stasis gene(SlSOS1).We further identified two VQ-motif containing proteins SlVQ16 and SlVQ21 as SlWRKY57-interacting proteins.SlVQ16 pos-itively,while SlVQ21 negatively modulated tomato resistance to salt stress.SlVQ16 and SlVQ21 com-petitively interacted with SlWRKY57 and antagonis-tically regulated the transcriptional repression activity of SlWRKY57.Additionally,the SlWRKY57-SlVQ21/SlVQ16 module was involved in the pathway of phytohormone jasmonates(JAs)by interacting with JA repressors JA-ZIM domain(JAZ)proteins.These results provide new insights into how the SlWRKY57-SlVQ21/SlVQ16 module finely tunes tomato salt tolerance.

Seed weight is usually associated with seed size and is one of the important agronomic traits that determine yield.Understanding of seed weight control is limited,especially in soybean plants.Here we show that Glycine max JASMONATE-ZIM DOMAIN 3(GmJAZ3),a gene identified through gene co-expression network analysis,regulates seed-related traits in soybean.Over-expression of GmJAZ3 promotes seed size/weight and other organ sizes in stable trans-genic soybean plants likely by increasing cell proliferation.GmJAZ3 interacted with both G.max RESPONSE REGULATOR 18a(GmRR18a)and GmMYC2a to inhibit their transcriptional activation of cytokinin oxidase gene G.max CYTOKININ OXIDASE 3-4(GmCKX3-4),which usually affects seed traits.Meanwhile,the GmRR18a binds to the promoter of GmMYC2a and activates GmMYC2a gene expression.In GmJAZ3-overexpressing soybean seeds,the protein contents were increased while the fatty acid contents were reduced compared to those in the control seeds,indicating that the GmJAZ3 affects seed size/weight and compositions.Natural variation in JAZ3 promoter region was further analyzed and Hap3 promoter correlates with higher promoter activity,higher gene ex-pression and higher seed weight.The Hap3 promoter may be selected and fixed during soybean domestication.JAZ3 orthologs from other plants/crops may also control seed size and weight.Taken together,our study reveals a novel molecular module GmJAZ3-GmRR18a/GmMYC2a-GmCKXs for seed size and weight control,providing promising targets during soybean molecular breeding for better seed traits.

Jasmonates(JAs)are phytohormones that finely regulate critical biological processes,including plant development and defense.JASMONATE ZIM-DOMAIN(JAZ)proteins are crucial transcrip-tional regulators that keep JA-responsive genes in a repressed state.In the presence of JA-Ile,JAZ repressors are ubiquitinated and targeted for degradation by the ubiquitin/proteasome system,allowing the activation of downstream tran-scription factors and,consequently,the induction of JA-responsive genes.A growing body of evi-dence has shown that JA signaling is crucial in defending against plant viruses and their insect vectors.Here,we describe the interaction of C2 proteins from two tomato-infecting geminiviruses from the genus Begomovirus,tomato yellow leaf curl virus(TYLCV)and tomato yellow curl Sardinia virus(TYLCSaV),with the transcriptional repressor JAZ8 from Arabidopsis thaliana and its closest orthologue in tomato,SlJAZ9.Both JAZ and C2 proteins colocalize in the nucleus,forming dis-crete nuclear speckles.Overexpression of JAZ8 did not lead to altered responses to TYLCV in-fection in Arabidopsis;however,knock-down of JAZ8 favors geminiviral infection.Low levels of JAZ8 likely affect the viral infection specifically,since JAZ8-silenced plants neither display ob-vious developmental phenotypes nor present dif-ferences in their interaction with the viral insect vector.In summary,our results show that the geminivirus-encoded C2 interacts with JAZ8 in the nucleus,and suggest that this plant protein exerts an anti-geminiviral effect.

茉莉酸(jasmonic acid,JA)能诱导青蒿素生物合成,为进一步解析青蒿JA信号通路,本研究从青蒿中克隆并鉴定2个JA信号通路中的负调控因子JAZ(jasmonate ZIM-domain)基因,分别命名为AaJAZ5和AaJAZ6.这两者均含有JAZ家族特有的保守区域ZIM和Jas.AaJAZ5在叶中表达量最高,其他部位的表达量较低;AaJAZ6在根中的表达量最高,茎中的表达量最低.茉莉酸甲酯(MeJA)和机械伤害处理都能显著提高AaJAZ5和AaJAZ6的表达.通过双分子荧光互补(bimolecular fluorescence complementation,BiFC)证明,AaJAZ5和AaJAZ6均能与AaMYC2相互作用,而只有AaJAZ5与AaCOI1存在相互作用,表明AaJAZ5在JA信号通路中可能具有更加重要的作用.本研究为进一步分析青蒿JAZ家族成员的功能分化和JA信号调控青蒿素生物合成的分子机制奠定了基础.

Hpa1是一种Harpin蛋白,可诱导植物的防御响应机制.以欧洲花楸悬浮细胞为材料,研究Hpa1粗提物(Hpa1 CE)对其次生代谢产物合成的影响以及茉莉酸(jasmonate,JA)信号通路是否参与相关信号的传导.结果显示,Hpa1 CE可诱导欧洲花楸细胞合成植保素,主要是异欧花楸素及其糖苷;Hpa1 CE处理使细胞内茉莉酸甲酯(MeJA)合成增加,同时细胞内异欧花楸素大量合成.向欧洲花楸细胞中同时添加Hpa1 CE和JA通路抑制剂salicylhydroxamic acid(SHAM),与Hpa1 CE组相比,细胞内合成的MeJA和异欧花楸素的量都大为降低.实时荧光定量PCR结果显示Hpa1 CE诱导后,JA通路中JAZ表达下调而myc2表达上调.因此Hpa1 CE处理导致欧洲花楸悬浮细胞建立了防御机制,茉莉酸通路参与了Hpa1 CE诱导的欧洲花楸细胞内植保素的生物合成.该研究首次从植物次生代谢的角度研究茉莉酸通路在植物防御机制中作用,为全面理解植物应激响应机制提供了线索.

Jasmonates (JAs) are cyclic fatty acid-derived phytohormones that regulate diverse aspects of plant defense and development.The endogenous active JA molecule (+)-7-iso-JA-L-Ile (JA-Ile) and its analog coronatine trigger formation of a complex with the F-box protein COI1 and JAZ repressors to induce degradation of the JAZs through the 26S proteasome pathway in a COI1-dependent manner.To reveal the formation process of COI1-JA-JAZ ternary complex,we employed several biochemical approaches to examine how JA is dynamically perceived.These analyses showed that the COI1 proteins of Arabidopsis and rice bind JA with appreciable binding affinity and revealed the kinetics and thermodynamics of the COI1-JA-JAZ ternary complex.Our results suggest that COI1 is the primary receptor perceiving the active JA molecule to initially form a COI1-JA complex that subsequently recruits JAZs for further signal transduction.

JAZ proteins are negative regulators of jasmonate responses,acting both as repressors of transcription factors and as co-receptors of JA-Ile.The high redundancy of JAZ genes in angiosperms has hindered the characterization of a complete depletion of JAZ function.Moreover,the recent discovery that dnOPDA is the jasmonate ligand in Marchantia polymorpha demonstrates that JA-Ile is not the sole COI1/JAZ ligand in land plants and highlights the importance of studying JAZ co-receptors in bryophytes.Here,we have exploited the low gene redundancy of the liverwort M.polymorpha to characterize the single MpJAZ in this early diverging plant lineage.We clarify the phylogenetic history of the TIFY family,demonstrate that MpJAZ is the ortholog of AtJAZ with a conserved function,and characterize its repressor activity of dn-OPDA responses.Our results show that,consistent with previous findings in Arabidopsis,MpJAZ represses jasmonates biosynthesis,senescence,and plant defenses,and promotes cell growth and reproductive fitness,highlighting the power of studies in Marchantia.

The many roles of jasmonate in plant growth,reproduction,and defense raise interesting questions about how this lipid-derived hormone emerged during evolution.Recent studies indicate that a "higher plant" pathway involving jasmonoyl-L-isoleucine (JA-lle) as the receptor-active ligand is conserved in vascular plants (Bowman et al.,2017;Howe et al.,2018).Within this core signaling pathway,JAZ proteins link JA-Ile perception to changes in the activity of MYC transcription factors (TFs) (Figure 1) and have emerged as a conserved hub for crosstalk in hormone response pathways.Therefore,understanding how JAZ proteins work across the plant tree of life is relevant to broad areas of plant biology.